Question 1

How to integrate FF4J with Spring Boot?

Accepted Answer

Add the ff4j-spring-boot-starter dependency, which auto-configures the web console and REST API. You'll need to configure a database store, and the starter handles most setup, including AOP support for annotations.

Question 2

FF4J vs LaunchDarkly for Java feature flags

Accepted Answer

FF4J is open-source and self-hosted, ideal for teams wanting control and avoiding vendor lock-in. LaunchDarkly is a managed service with more analytics but costs money. Choose based on budget and infrastructure preferences.

Question 3

Can FF4J be used without a database?

Accepted Answer

Yes, for development, it supports in-memory stores, but production use requires a database for persistence, audit trails, and to avoid data loss on restarts. The README emphasizes multi-database support for scalability.

Question 4

How to secure the FF4J web console?

Accepted Answer

Integrate with Spring Security or similar frameworks to add authentication and authorization. The web console is a servlet, so you can apply security filters as per your app's setup, but this requires manual configuration.

Question 5

Does FF4J support feature flags for JavaScript frontends?

Accepted Answer

Yes, through the REST API, frontend apps can query feature statuses. However, you must manage API endpoints, CORS, and security, as FF4J is backend-focused with no built-in frontend SDKs.

Question 6

How to implement custom toggle strategies in FF4J?

Accepted Answer

Extend the AbstractFlipStrategy class, implement the evaluate method, and register it in FF4j configuration. The README mentions support for custom predicates like time-based or Drools rules.

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